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Sunday, June 19, 2011

Guess The Genotype #1

This is something that I find rather fun. Take a dog (or cat) with an interesting color and guess the genotype. This is especially fun when looking at mixed breeds because it can often lead to guesses as to what the dog's ancestry may be. To begin this, I will be looking at Charlie. He was my family's loving companion for fifteen years. We had to put him down in March of 2010 after it was discovered that he had a very aggressive form of cancer. I played guess the genotype and guess the breeds many times over the years, and this is what I concluded: he was a recessive red piebald with liver pigmentation and ticking. What breeds? I'm still a bit unsure, but from his appearance, plus where we adopted him (rural Mississippi where nearly all of the dogs are hunting/sporting types or pit bulls) my best guess is Labrador, Brittany, and beagle with possibly a little bit of something else thrown in. Here's the breakdown:

Charlie's nose, eye rims, lips, and paw pads were definitely not black, instead being distinctly brown in color. This led me to conclude that he was recessive bb liver. Liver (also called "brown"/chocolate/red depending on the breed is found on the "B" locus) will dilute all black on a dog's body to brown.

Charlie had only red and white hairs with no hint of brown hairs, this led me to conclude he was ee recessive red. Recessive red (also called "extension" is found on the "E" locus) prevents black or the dilutions there of from being expressed in the coat, turning it a solid red color, though the red can vary greatly in shade from deep mahogany red to nearly white in color. Charlie is on the dark end of red, but since there is a lot of question as to what genes affect the intensity of red, I won't go into that. Sable red, though it can often be nearly all red in color, usually has at least some hint of black or its dilutes in the coat.

Charlie had a significant amount on white on his coat. It did break his topline and covered over 50% of his body, making it clear he was recessive spsp piebald spotting. Piebald (found on the "S" or "spotting" locus) affects all other colors on a coat, leaving patches of white. Piebald is recessive to the solid (S) gene, as well as the Irish white gene (si) and is dominant to the extreme white piebald gene (sw). Though it is possible he carried a gene for extreme white piebald, I doubt it. Usually the recessives a dog carries on the S locus will in fact effect the overall amount of white. The most famous example of this is in Boxers, which have two genes on this locus: S and sw, yet show three distinct phenotypes: SS solid, swsw white, and Ssw which appears Irish white. Since Charlie showed such classic mid-grade piebald spotting, he was most likely spsp.

Charlie also had small spots of color randomly distributed throughout his coat. This made me conclude he was homozygous Tt ticked. Ticking (found on the "T" locus) is a dominant gene, with the recessive being no ticking. Since his ticking was not very dense, I suspected that he only had one copy of the dominant gene. When a dog has heavy ticking, I would suspect it to be TT, and thus Charlie probably was not.

It is interesting to note that a mixed breed showed so many recessive genes, but, depending on ancestry, this is very possible. I suspect that he was Labrador/Brittany/beagle partly because of his color and also partly because of his looks. He had a mostly Labrador head, size, and coat, though less oily and maybe a bit longer. Labradors also come in both liver (chocolate) and recessive red (yellow). His tail set, which was nearly always held perfectly upright, is very beagle, and beagles come in recessive red, piebald, ticked, and liver (though ticking and liver are most often seen in working lines, but because of where he came from this is not unlikely). He also had roughly the body type of a Brittany, and Brittanys come in recessive red, liver, piebald, and ticked.

No matter what, we loved him and miss him.

For the next Guess the Genotype, I'll be posting a picture and have you guys guess, then I'll post my opinions.

1 comment:

I read your blog with big interest! Can you tell me how I can learn about the color genetics in dogs? I LOVE great danes and I would love to know EVERYTHING about their colors and how colors can be if you mix them :) Thank you!